Fertilizing
Feed from leaf-out until late summer, then stop so the new wood can harden before winter. Do not feed while the tree is dormant.
- Use solid organic fertilizer once a month or liquid fertilizer every one to two weeks.
- Switch to a low-nitrogen fertilizer in late summer to support next year's flower buds.
- If leaves turn pale yellow with green veins, add an iron fertilizer; the kousa dogwood is most prone to this.
Placement
Keep your dogwood bonsai outdoors all year, in full sun to light shade with good air circulation. In hot summers, give the kousa dogwood shade in the afternoon to prevent leaf scorch.
The tree needs winter cold to rest and to flower. Protect the roots in a cold frame, an unheated shed or by burying the pot when temperatures fall below -10°C (14°F).
Pruning
Next year's flower buds form during summer: round, plump buds are flower buds, slim pointed ones are leaf buds. Do the main pruning right after flowering, so new growth has time to set buds.
- Let new shoots grow four to five leaf pairs, then cut back to one or two pairs.
- Finish shoot trimming by midsummer; later cuts remove next year's flowers.
- In late winter, remove only crossing, dead or badly placed branches, sparing the flower buds.
Avoid heavy pruning in late summer and autumn, which triggers soft growth that will not harden before winter. Wire young branches in spring or summer and check often, as they thicken quickly.
Repotting
Repot young trees every 2–3 years and older ones every 3–5 years. Repot in early spring as the buds swell; the cornelian cherry and Japanese cornel, which flower on bare wood, can also be repotted right after flowering.
- Use a well-draining mix such as equal parts akadama, pumice and lava.
- The kousa dogwood prefers slightly acidic soil, while the cornelian cherry tolerates lime.
- Trim no more than a third of the roots.
Watering
Water thoroughly as soon as the top layer of soil begins to dry, and never let the root ball dry out. In summer this often means daily watering, especially for the drought-sensitive kousa dogwood.
Avoid waterlogged soil, as constantly wet roots rot. In winter the dormant tree needs much less water, but keep the soil slightly moist. If your tap water is very hard, use rainwater for the kousa dogwood.
Seasonal care
- Spring: The cornelian cherry and Japanese cornel flower on bare branches; repot as buds swell or right after flowering. Start feeding once the leaves unfold and let new shoots grow.
- Summer: The kousa dogwood flowers in early summer. Trim new shoots back to one or two leaf pairs, finishing by midsummer, water daily if needed and give afternoon shade in hot weather.
- Autumn: Enjoy the red fruits and autumn colour, and switch to low-nitrogen feed in late summer, then stop. Avoid heavy pruning so the new wood can harden.
- Winter: Leave the tree outdoors to rest in the cold, and protect the roots below -10°C (14°F). Water sparingly and do only light structural pruning, sparing the round flower buds.
Common problems
Dogwoods are tough trees, but a few problems come up regularly.
- No flowers: Usually caused by pruning after midsummer or in winter, which removes the flower buds. Prune right after flowering and keep the round flower buds when tidying in winter.
- Leaf scorch: Brown, crispy leaf edges in hot sun or after the soil dries out, mostly on the kousa dogwood. Give afternoon shade and check the soil daily in summer.
- Powdery mildew and leaf spot: White coating or dark spots on the leaves in humid, still weather. Improve air circulation, water the soil rather than the leaves and remove infected leaves.
- Chlorosis: Yellow leaves with green veins in alkaline soil or with hard water. Use slightly acidic soil, water with rainwater and add an iron fertilizer.
- Aphids and scale: Sticky leaves and curled young shoots in spring and summer. Rinse off aphids and treat scale with horticultural oil.